NFB24-S Belimo Actuator


Damper Actuator, 90 in-lb [10 Nm], Spring return, AC/DC 24 V, On/Off, 2 x SPDT (NFX24-S)

10 in stock


Spring, 90in-lb, On/Off, 24V, SW (NFX24-S)


Installation Guide


For On/Off, fail-safe control of dampers in HVAC systems. Actuator sizing should be done in accordance with the damper manufacturer’s specifications. Control is On/Off from an auxiliary contact or a manual switch. The actuator is mounted directly to a damper shaft up to 1.05” in diameter by means of its universal clamp. A crank arm and several mounting brackets are available for applications where the actuator cannot be direct coupled to the damper shaft.


The NF..24-S series actuators provide true spring return operation for reliable failsafe application and positive close off on air tight dampers. The spring return system provides constant torque to the damper with, and without, power applied to the actuator. The NF..24-S series provides 95° of rotation and is provided with a graduated position indicator showing 0° to 95°. The actuator may be stalled anywhere in its normal rotation without the need of mechanical end switches. The NF..24-S versions are provided with two built-in auxiliary switches. These SPDT switches are provided for safety interfacing or signaling, for example, for fan start-up. The switching function at the fail-safe position is fixed at 10°, the other switch function is adjustable between 10° to 90°. The NF..24-S actuator is shipped at 5° (5° from full fail-safe) to provide automatic compression against damper gaskets for tight shut-off.


  • Actuator Type
    • Spring return
  • Angle of Rotation
    • 95°
  • Auxiliary Switches
    • 2 x SPDT
  • Control Type
    • On/Off
  • Degree of Protection
    • IP54, NEMA 2, UL Enclosure Type 2
  • Direction of Rotation (Fail-Safe)
    • Reversible with cw/ccw mounting
  • Electrical Connection
    • Cable
  • Manual Override
    • 5 mm hex crank (3/16″ Allen), supplied
  • Power Consumption (Holding)
    • 5 W
  • Power Consumption (Running)
    • 6 W
  • Running Time (Fail-safe)
    • <20 s
  • Running Time (Motor)
    • 75 s
  • Safety Function
    • YES
  • Shaft Diameter
    • 1/2…1.05″ round, centers on 1/2″ and 3/4″ with insert, 1.05″ without insert
  • Torque
    • 90 in-lb [10 Nm]
  • Voltage AC/DC
    • AC/DC 24 V

Additional information

Weight 8 lbs
Dimensions 2 × 2 × 2 in
Part Number